Apparatus for the purification of metals



g- 1965 R. JACQUE$ 3,261

APPARATUS FOR THE PURIFICATION OF METALS Filed Aug. 2, 1962 INVENTOR ROLAND JACQUES 5m M2 & 632

ATTO

United States Patent 3,201,101 APPARATUS FOR THE PURIFICATION OF METALS Roland Jacques, Paviilons-sous-Bois, Seine, France, assignor to Les Produits Semi Conducteurs, Paris, France Filed Aug. 2, 1962, Ser. No. 214,363 Claims priority, application France, Aug. 3, 1961, 869,937 4 Claims. (Cl. 266-9) This invention relates to antimony of extremely high purity, to a method of making it and to an apparatus for making it.

It is known that relatively pure antimony can be produced by reducing antimony chloride by reducing gases such as hydrogen, but the process, as carried out by the classic method and classic apparatus, does not generally produce antimony of great purity. The highest-purity antimony is generally thought to be electrolytic antimony.

It is an object of this invention to produce antimony of purity as high or higher than that which is obtained by the electrolytic process. Another object is to produce such antimony by chemical as distinguished from electrolytic processes. Another object of the invention is to produce apparatus of relatively simple design which is capable of carrying out not only the purification of antimony but the reduction of vaporizable metal salts in general.

The objects of the invention are accomplished, generally speaking, by antimony having a ratio of resistivity of about 6.2750 when compared at 0 C. and at the temperature of liquid nitrogen; by a method of producing Sb of high purity that comprises refluxing relatively pure SbCl distilling ofi H 0 and its HCl azeotrope, and some heads of SbCl distilling off the main fraction of SbCl and isolating it, vaporizing it in reducing atmosphere, flowing the vapors through a zone of increasing temperature in which the vapors are progressively solidified and melted, and flowing the molten antimony to a zone at solidifying temperature; and by an apparatus for purifying metals such as antimony, or for reducing their salts, which comprises a receptacle adapted to contain metal salts such as antimony chloride, an elongated reaction chamber connected to the receptacle by a measuring connection, means to heat the reaction chamber throughout its length to a temperature at which antimony chloride, or other salts, will vaporize, means to heat a localized part of the reaction chamber to a higher temperature, at least the reaction temperature of salt, and means to fill the reaction chamber with reducing gas.

The apparatus, which is an object of this invention, produces an extremely high rectification of antimony chloride, which is the preferred raw material, and produces antimony which is very pure and practically free of arsenic, which constitutes the impurity which is most frequently found and most difficult to eliminate.

The apparatus includes a rectification column, a reducing chamber and heating means for it which includes a fixed and a movable heat source. The apparatus eliminates any manipulation of intermediate products. The following description is of a preferred apparatus which is diagrammatically described in the accompanying drawing.

In this drawing a heating means 10 receives a flask 11 which is provided with a filling trap 12 and a temperature measuring device '13. Attached to the neck of the flask 11 is a rectifying column 14 which is heated by a series 15, 16, 17, 18 of independently controllable heaters which provide for the accurate control of the temperature of the rectifying column throughout the major portion of its height. Atthe upper end of the rectifying column is a cooler 19 which can insure the conice densation of any gases which pass above the heated portion of the column during refluxing. The heaters 15, etc., are enclosed in insulation, for instance, glass wool. Near the top of the column 20 there is attached a condenser tube 21 served by a valve 22 which is encircled by a heating coil 23 and is divided in two parts 24, 25, controlled by valves 26, 27, respectively. At the bottom of tube 24 is a receptacle 28 and at the bottom of tube 25 is a receptacle 29. Valve 22 permits the confinement of the materials to the column during the period of reflux, and the valves 27, 28 permit the distillate to be directed to flask 28 or to flask 29 as desired.

Flask 29 is provided with internal heater 30 and at its bottom receives the rays of infra-red heater 31. At its bottom this flask is provided with a dropper 32, or other type of measuring feeder, which is in tight connection with a neck 33 on the reduction chamber 34.

The reduction chamber is in an elongated tube which is encircled by a heating coil 35 which extends throughout its length and serves to maintain it at a selected temperature, and it is also acted upon by a movable heater 36 which is mounted on rails 37 and can be moved along the chamber to bring any desired portion of it to a temperature higher than that which is provided by the winding 35. At one end, the reduction chamber is in communication with a tube 38, which can be supplied on the one hand with an inert gas through tube 39, and on the other hand with a reducing gas through tube 40. The gases are indicated as argon and hydrogen, respectively, in the drawing. At its other end the reduction chamber is provided with a tube 41 which permits its content of air to be scavenged by gas flowing through pipe 38.

Assuming that the device is being used for the purification of antimony, antimony chloride of relative purity is admitted to the flask 11 and is subjected to refluxing in the column 14 for an adequate period, during which water and its azeotrope with HCl are driven ofl through the condenser 19. The valves 22 and 26 are then opened, the valve 27 remains closed, and the head of antimony chloride, for instance 10%, is condensed in the flask 28. After this head has been removed the valve 26 is closed, the valve 27 is opened and the SbCl is delivered to the flask 29, in which it is maintained at a temperature near C. In the meantime, the reaction chamber 34 has been prepared by opening the line 39 to argon, or some other inert gas, which sweeps the air out of the reaction chamber. Thereafter, the argon may be turned off and the hydrogen admitted or they may be admitted in admixture, and the reaction chamber is heated at the zone nearest the flask 29 to a temperature at which antimony chloride is vaporized, for instance 250 C. The heater 36 is moved some distance away from the inlet 33 and is heated to about 700800 C., bringing the zone of the reaction chamber which is within it to comparable temperature. There is thus established a minimum temperature of 250 C. at the inlet and a maximum of possibly 750 C. inside the heater 36. The heater may be placed, for example, 25 cm. away from the inlet. The antimony chloride is admitted drop by drop to the inlet end of the reaction chamber 34, and is vaporized. The vapors mingle With the reducing atmosphere and move toward the heater where they undergo reduction and are solidified as needles on the walls of the reduction chamber. When the solid antimony deposits approach closely enough to the heater 36 they are melted and will flow along the reduction chamber to its discharge end, the chamber being tilted for that purpose. The metal solidifies and forms an ingot which can eventually be removed.

The apparatus may be made of glass and fused quartz, the reduction chamber being preferably fused quartz.

The joints in the apparatus may be of some inert plastic such as polytetrafluoroethylene.

The source of hydrogen should furnish pure hydrogen and for this purpose an Engelhard apparatus operating by the diffusion of hydrogen through palladium at 350 C. is useful.

In obtaining the relatively pure antimony chloride which is used as the raw material in flask 11, one takes antimony oxide, attaclcs it with hydrochloric acid, distills the product in reducing medium, for example in the presence of hydrazine chlorohydrate, and expels water and its azeotrope with HCl, leaving antimony in the flask. To this there is added commercial HCl and distillation is continued until the sulfur has been removed as H 8. The product is then distilled to eliminate the head ends, which constitute about of the antimony chloride in the flask.

The relatively pure antimony chloride thus obtained is admitted to the flask 11 and is refluxed for about 2 hours. The distillation proceeds drop by drop, to the elimination of the water and its HCl azeotrope, without interrupting the heating, which proceeds from about 110 to 200 during this operation. The operation is then pursued by activatin gtheheaters 15, 16, 17, 18, which pass the, heads of antimony chloride to the flask 28. The major fraction of the antimony chloride is then distilled into flask 29. The hydrogen is brought, in its Eng'elhard purifier, to about 350 C. and is sent with argon through the tube 38 to sweep outthe reaction chamber. The heater 36 is raised to 63 0 C. at its left end. When the reaction tube has. been purged, the argon is turned off and pure hydrogen is admitted to the inlet, which is maintained at 250 C. throughout the operation, the hydrogen being reduced to about that temperature during its passage through tube 38. The valve 33 is opened slightly to allow the antimony chloride to drop into the reaction chamber. The reduction is carried out at a temperature of 700800 C. At the beginning of the reduction there is formed in reaction chamber 34, between the heater 36 and the inlet, a deposit of antimony needles which filter the later formed particles of anti- 7 mony. As soon as this deposit is thick enough, the input of antimony chloride may be increased to accelerate the process. The antimony deposit moves nearer and nearer to the hot zone of the furnace. At the same time, when the deposit approaches closely enough to a zone which is very hot, the antimony melts in the tube and runs toward the low point of the tube where it is solidified as an ingot. To stop the operationin the tube, the valve 33 is closed and the heater 36 is moved to a position which melts the antimony which has collected on the wall near the inlet, the tube is cooled, the hydrogen is turned off, and argon is passed through the tube for several minutes. The antimony ingot can be removed by removing the end 42 of the tube which is mounted in position by means of a polytetrafluoroethylene sleeve 43. v A substantial advantage of the invention is that the apparatus prepares very pure antimony witha reduced number of operative steps and without any manipulation of the-product. The process is substantially self-operating and a material improvement over known processes.

The following example illustrates the invention without imposing limitations on the generalities of what is elsewhereherein stated and claimed.

Example quantities. This was introduced into a reaction vessel in a proportion of 5 kg. of antimony oxide to 15 liters of commercial HCl. It was agitated 24 hours, decanted and distilled with 100 grams. of hydrazine chlor hydrate, This eliminated the water and its HCl azeotrope, which passed on. at about 200 C. A mixture of sulfur and sulfide was deposited in the condenser. The operation was stopped and 2 liters of HCl were added; distillation continued until the sulfur was eliminated, passing off as H 8. Distillation continued until the heads had been removed and the bulk ofthe antimony chloride was re tained. This is the relatively pure antimony chloride which is employed in the novel apparatus as the raw material. This was placed in the flask 11 of the apparatus. 600 to 700 grams of antimony chloride were distilled to the flask 28 and the rest of it, 5.5 kg. was disstilled into flask 29.

The heater 36 was heated to 750 C. and placed 25 cm. from the inlet. The reaction chamber was swept clear by argon and the hot hydrogen was turned on to fill the chamber. As soon as the temperature of the inlet (the part of the vaporizer where the chloride is vaporized) was sufficient, the chloride was admitted in one drop in two seconds while the hydrogen was admitted at 20' liters per hour. In the first hour black antimony needles formed on the walls between the heater and the inlet. The chloride was then addedat a rate of 1 drop per second, and the deposit of metallic antimony was increased and progressed little by little toward the heater. When it reached the zone of the tube which was at 630 C., it melted and ran down the tube through the heater at the other end. Thus, in four hours there was prepared an ingot of very pure antimony. The operational efliciency is about the antimony ingots obtained are 5 mm. thick and 15 mm. wide. Its content of impurities was not over:

Parts per million Copper l Arsenic 3 Nickel 1 Aluminum 2 Bismuth 2 The antimony thus obtained is considered as ultra pure, which is attested by the results of electrical resistivity test. If one compares the ratio of resistivity at 0 with that of the temperature of liquid nitrogen one obtains a ratio of 5.9728 for electrolytic antimony, the purest heretofore known, which corresponds to 99.999% purity. The antimony-prepared according to the present invention has a ratio of resistivity of 6.2750, which is superior to that of electrolytic antimony and is accordingly a purer and superior product.

As many apparently widely different embodiments of the present invention may be made without departing from the spirit and scope thereof, it is to be understood that the invention is not limited to the specific embodiments.

What is claimed is:

1. Apparatus for the purification of metals, especially antimony, comprising a reflux still, a condenser, and a receptacle capable of holding antimony chloride, means to heat the receptacle, a tubular reaction chamber at tached to the receptacle by a valve, means to supply the reaction chamber with inert and reducing gases, means whereby the chambermay be scavenged by the inert gases, means to heat the reaction chamber more or less uniformly throughout its length, and a second heating means movable along the reaction chamber adapted to heat a localized part thereof to higher temperature than that provided by the first heating means;

2. Apparatus for purifying metals such as antimony which comprises a heated receptacle adapted to contain metal salts such as antimony chloride, an elongated reaction chamber connected to the receptacle by a dropper, means to heat the reaction chamber throughout its length to a temperature at which antimony chloride will vaporize, means to heat a localized part of the reaction chamber to the reducing temperature of antimony chloride, and means to fill the reaction chamber with reducing gas.

3. Apparatus adapted to the production of pure antimony substantially consisting of a distillation vessel adapted to receive antimony chloride, a rectification column provided with a sequence of individually controllable heaters along its length, discharge means connected to the column adapted to the release of gases, condenser means connected to the columns provided with heating means, a first discharge for the condenser, a second discharge for the condenser including a heated conduit and a receptacle, an elongated reaction chamber connected to the receptacle and to sources of inert gas and of reducing gas, fixed heating means embracing the reaction chamber throughout a substantial length thereof, movable heating means embracing the reaction chamber through a lesser length thereof, and means to extract a product from the reaction chamber.

4. Apparatus adapted to the production of pure Sb comprising in interconnected sequence distillation means, rectification means having stages of controllable temperature, heated condenser means, flow control means for the condensate from the condenser, a reaction chamber having fixed heating means and movable heating means, means to supply the reaction chamber With gases, and means to discharge the reaction chamber.

References Cited by the Examiner UNITED STATES PATENTS 1,799,102 3/31 Kelley 13-5 2,366,881 1/45 Telkes 75149 2,596,100 5/52 Listra't 75-69 2,615,706 10/52 Davey 266-49 2,710,253 6/55 Willardson 75149 2,944,885 7/60 Wollf 75-69 3,006,734 1'0/ 61 Cowlard et a1 23-277 X 3,039,755 6/62 Mehal 266-19 MORRIS O. WOLK, Primary Examiner.

DAVID L. RECK, WINSTON A. DOUGLAS, JAMES H. TAYMAN, JR., Examiners. 

1. APPARATUS FOLR THE PURIFICATION OF METALS, ESPECIALLY ANTIMONY, COMPRISING A REFLUX STILL, A CONDENSER, AND A RECEPTACLE CAPABLE OF HOLDING ANTIMONY CHLORIDE, MEANS TO HEAT THE RECEPTACLE, A TUBULAR REACTION CHAMBER ATTACHED TO THE RECEPTACLE BY A VALVE, MEANS TO SUPPLY THE REACTION CHAMBER WITH INERT AND REDUCING GASES, MEANS WHEREBY THE CHAMBER MAY BE SCAVENGED BY THE INERT GASES, MEANS TO HEAT THE REACTION CHAMBER MORE OR LESS UNIFORMLY THROUGHOUT ITS LENGTH, AND A SECOND HEATING MEANS MOVABLE ALONG THE REACTION CHAMBER ADAPTED TO HEAT A LOCALIZED PART THEREOF TO HIGHER TEMPERATURE THAN THAT PROVIDED BY THE FIRST HEATING MEANS. 